To be honest, once a week probably won't do an awful lot. If it's for general fitness, either to maintain weight or to keep off fat when bulking, you'd be better served running three times a week or so.

If it's for cutting (ie. losing weight) you could up that to four or five times a week.

Add some cardio to your workout after your weights, twenty minutes upwards, depending on what you think. Try three to four times a week and see how you do. Some find this is enough, some need more. If you feel you are putting on too much fat then increase the session time.